ReferenceError and the global object

Question

In javascript window is the global object, which means every object in the global scope is a child of window. So why I get this resul

Answer 1

In your first example (window.foo) you are accessing a property of the window object. JavaScript returns "undefined" for when you are trying to access a non existent property of a object. It's designed that way.

In the second example you are referencing a variable directly, and since it does not exists an error is raised.

It's just the way JavaScript is designed and works.